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Dr. Hamman
Dr. Hamman, Automotive Engineer
Category: Car
Satisfied Customers: 6286
Experience:  30 years experience, Repairing, building, & designing, automobiles.
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1973 corvette: It slips out of 3rd gear when decelarating

Customer Question

I have a 1973 corvette with a munci 4 speed. It slips out of 3rd gear when decelarating. What causes that.
Submitted: 6 years ago.
Category: Car
Expert:  Dr. Hamman replied 6 years ago.
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Dr. Hamman :

Hi, I will do my best to assist you. When you are finished please click on accept. I don't get paid unless you do. I don't know if you are a pro or a novice so we may have to fine tune the answer. I only know as much about your problem as you have told me in your post, so my answer will be based on what you have posted. Feel free to add any additional info you feel is needed.



Normally this is wear in the 3-4 slider, and the 3rd gear drive gear. In 3rd there is a drive gear, and a driven 3rd gear, and the 3rd drive gear engages with the 3- 4 slider and should pop into place where it stays and gives you 3rd until you shift. Upon rare occasion the detents that help hold the 3- 4 slider into place will be bad and the gears will be good, but it is almost always the 3rd drive gear and the 3-4 slider causing the problem. BotXXXXX XXXXXne is the transmission has to come out and apart to fix this type of problem. Also this type of problem normally circulates steel fragments from the damage, and this is real bad on the other gears. If you catch it early enough the damage is normally isolated to the parts discussed. If you have any more questions I am here to help. Good luck, and Thanks for using Just Answer.


I hope this helps, 100% satisfaction is my goal. If the answer is not clear, please reply and I will assist you more. When you're satisfied, click on accept. I don't get paid unless you do. A bonus and positive feedback are always appreciated, good luck and Thanks.


 

Customer:

Hello, Sorry it has taken me so long to respond. Can you send me a blow-up picture of the gear case and point out exactly what parts you are talking about. You are using terminology that I cant find in the references I am using. Thankyou

Dr. Hamman :

I don't have a blow up, sorry about the terminology gap. The slider is the piece the shift fork engages into. The slider gets pushed towards the synchro when you shift, captures the synchro, and then the gear (drive gear) to complete the shift into the gear you choose. The driven gear it the gear the drive gear is meshes with and turns or drives. The drive and driven gears are always in contact with each other, but they are not locked in to the power from the engine until the slider captures one of the drive gears to put the trans into gear, all the other gears are in contact, but they freewheel, until you choose that gear and the slider locks into position to complete the shift. The detents are spring loaded pieces that prevent the slider form moving around on its own, and their job is to help the slider locked into position when you make a shift to keep the trans from jumping out of gear. Good luck, and Thanks for using Just Answer.


I hope this helps, 100% satisfaction is my goal. If the answer is not clear, please reply and I will assist you more. When you're satisfied, click on accept. I don't get paid unless you do. A bonus and positive feedback are always appreciated, good luck and Thanks.